Where one who is lucky enough to possess long vagina flaps, squats over her unknowing prey - usually asleep, passed out or even dead, and proceeds to dunk, stroke and caress her trailing labia into any available cervice or indeed hole of the human face. The mouth and eye sockets are the most desired areas to scrub upon.
Curtain washing (aka inverted teabag, kunt kissing) is a very rare maneuver and very few have had the pleasure of seeing it performed.

Leigh was so infuriated by the nights events she decided her satin curtains could do with a good wash to calm her down and the nearest thing to a washboard was that horrible boy's face.

Luke: Hey, have you ever seen your wife wash the curtains?
Matthew: No, my wife is a pussy, curtain washing is for the brave and fearless